Iodine Release

Refinements have been made on the source term calculational methods since WASH-1400. The general trend has been toward source term reduction (e.g., the iodine release for the large LOCA) as compared with the RSS results. In cases such as Station Blackout, the RSS underestimated the tellurium and barium compared with results from the BMI-2104 suite. 

The nuclear explosions that devastated Hiroshima and Nagasaki killed 100,000 to 200,000 people instantaneously. Probably an equal number died later, victims of the radiation released in those explosions. Millions of people were exposed to the radioactivity released by the accident at the Chernobyl nuclear power plant. The full health effects of that accident may never be known, but 31 people died of radiation sickness within a few weeks of the accident, and more than 2000 people have developed thyroid cancer through exposure to radioactive iodine released in the accident. Even low levels of radiation can cause health problems. For this reason, workers in facilities that use radioisotopes monitor their exposure to radiation continually, and they must be rotated to other duties if their total exposure exceeds prescribed levels. 

The amount of free iodine the solution can generate is termed the available iodine. This acts as a reservoir for active iodine releasing it when required and therefore largely avoiding the harmful side-effects of high iodine concentration. Consequently, when used for antisepsis, iodophors should be allowed to remain on the skin for 2 minutes to obtain full advantage of the sustained-release iodine. 

Theory Ti02 acts as photocatalyst due to generation of photoexcited electrons and holes which were involved in decomposition of KI. Under ultrasonic irradiation efficiency of iodine release increased almost linearly with irradiation time. 

The normality of the stronger solution is checked once a month in the following way 0.1 ml ethyl hydroperoxide solution +2 ml potassium iodide (20 g/100 ml) + 2 chops of glacial acetic add are placed in a porcelain crucible, covered with a lid, and allowed to stand at room temperature for 4 hours. The amount of iodine released is then titrated with 0.05 N sodium thiosulfate. 

The peroxide value (PV) of an oil or fat is defined as the quantity of peroxide oxygen present in the sample. This classical iodometric method is a volumetric analysis based on the titration of iodine released from potassium iodide by peroxides in a biphasic system using a standardized thiosulfate solution as the titrant and a starch solution as the indicator (see Background Information, discussion of peroxide value). This method will detect all substances that oxidize potassium iodide under the acidic conditions of the test, therefore the purity of the reagents is critical. 

Potassium iodide, which is used in unmeasured but excess amounts in iodo-metric titration, is the source of iodine for many types of reactions. It dissociates to iodide anion, which then reacts with the analyte to produce iodine. Hypochlorite reaction is shown below as an example. By measuring the amount of iodine released, the concentration of the analyte in the sample can be determined. 

The only iodides which are more insoluble than their hydroxide analogs are Hg(I), Ag, and T1. It should be mentioned that even though a compound has a less soluble hydroxide analog, the rate of conversion may be slow enough for the iodine release rate to be acceptable. 

Megaw, W.J. May, F.G. (1962) The behaviour of iodine released in reactor containments. Reactor Science Technology, 16, 427-36. 

The most likely fate of atomic iodine released into the troposphere by photodissociation of iodomethane is reaction 23 with ozone, but the subsequent reactions of iodine oxide are as yet unknown22. 

Other methods were developed for various anions. Bromides were oxidized with permanganate and the bromine so produced reacted with cyclohexene to form 1,2-dibromocyclohexane [577]. Similarly, iodides were analysed in milk as monoiodoacetone after oxidation with iodate and after reaction of the released iodine with acetone [578]. Pennington [579] utilized the same oxidation reaction for the analysis of iodates the iodine released was analysed as such. Cyanides were chlorinated prior to analysis with chloramine-T and the cyanogen chloride so produced was subjected to GC [580]. Analogously, cyanides and isocyanates form cyanogen bromide with bromine water, which can be analysed by GC [581]. 

The TM-2 accident was initiated by a sudden stop of some pumps in the secondary system. Some erroneous operations and the inferiority of some equipment enhanced the accident. About three hours after the initial incident, the primary water overflowed onto the floor of the auxiliary building, and the radioactivity in the primary water, especially xenon, krypton and iodine, were released into the atmosphere. In total, 10 Ci of noble gases were released into the atmosphere, whereas the total amount of the iodine release was 17 Ci. 

One per cent potassium iodide in neutral buffered or alkali solutions is more stable and useful than 20% potassium iodide in bubblers for collection and determination of ozone in air. Either 1 % solution may be used to determine low concentrations of ozone however, there is a difference in their stoichiometry. Over the range of 0.01 to 30 p.p.m. (v./v.) results by the alkaline procedure should be multiplied by 1.54 to correct for stoichiometry. The neutral reagent does not require acidification and has more nearly uniform stoichiometry. The alkaline procedure is preferable when final analysis may be delayed. Experiments with boric acid for acidification of samples in the alkaline reagent show that some mechanism other than oxidation of iodide to iodate or periodate is involved, possibly formation of hypoiodite. Preliminary experiments with gas phase titrations of nitrogen dioxide and nitric oxide against ozone confirm the stoichiometry of the neutral reagent as 1 mole of iodine released for each mole of ozone. 

Experimental evidence indicates that in strong alkali this pattern is not followed. When portions of samples in reagent III were acidified to pH 6.2 with solid boric acid, the iodine released was approximately 50% of that resulting from the usual acidification to pH 2. No iodine was obtained from reagent III with added iodate, upon acidification with boric acid. With added periodate, such acidification yielded 14 to 20% of the iodine obtained at pH 2. This compares with 25% reported for periodate by Willard and Merritt 11) A reasonable explanation of these data would appear to be the formation of hypoiodite by the following reaction ... 

Will be decomposed by air to WI2 and I2, is soluble in water, but hydrolyzes insoluble in ether and CHCI3, slowly soluble in cold alcohol chlorine replaces iodine at 18 °C, and bromine replaces it at 100 °C. Dissolution and iodine release occurs with KOH solutions, molten alkali carbonates, molten potassium bisulfide, and liquid potassium. 

CAUTION Iodine crystals are toxic and can stain the skin. Use care when using solid iodine. The reaction of zinc and iodine releases heat. Always use the test-tube holder to handle the reaction test tube. 

Mechanism of Action. TSH and LATS cause similar effects on glucose oxidation, P uptake (F2), and iodine release (E6). The time course is delayed, presumably due to the molecular size of the LATS. Antihuman TSH antibody did not inhibit the effect of LATS on P uptake into phospholipids or on glucose oxidation. As stated above (M13) proteolytic digestion of LATS makes it a short-acting thyroid stimulator. 

Even greater than this event, in terms of radioactive iodine release, was the cumulative release (Windscale... 

Blockade of thyroidal iodine release occurs at serum lithium levels between 0.6 and 1.2meq/l (Temple et al., 1972). The target concentration of lithium is generally achieved in 2-3 days if a loading dose of 600 mg is given, followed by 300mg three times daily (Koong et al., 1999) (Table 103.4). 

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